The present invention relates to a throttle for maintaining constant clearance in a gas bearing by pressure-dependent control of the throttle cross section.
As a rule, gas bearings have a throttle insert of adjustably fixed cross section by which gas flow can be adjusted, to thereby adjust the bearing pressure which determines the size of the bearing clearance. But the magnitude of bearing clearance is also dependent on the load acting on the bearing. Under varying loads the magnitude of the bearing clearance therefore changes continuously, and this is undersirable in certain cases of use, as for example when the bearings are used to guide movable parts in precision measuring machines or in machine tools.
Plain bearings are already known which have throttle inserts of adjustable cross section, the load-dependent bearing pressure effecting a change in the throttle cross section. For example, West German OS No. 2,538,226 and OS No. 2,548,385 disclose throttle inserts of elastomeric material, containing capillary bore passages for the supply of lubricant, in those cases oil for a radial bearing. These bore passages widen with the increase in bearing pressure which occurs upon heavier loading.
West German OS No. 1,943,833 describes an axial-plain bearing having a ring which is movable in response to bearing pressure and against spring force to control the cross section of a plurality of supply passages for the required lubricant.
These known throttle inserts are component parts of the specific bearing in which they are used, and their shape and construction are adapted and optimized to such bearing.
West German OS No. 2,514,370 discloses a device for adjusting the bearing clearance of gas bearings in which the temperature of the operating gas changes under control by the bearing pressure, to thereby effect a widening of contraction of the bearing nozzles. Such a control is relatively expensive and requires the use of special materials especially selected on the basis of coefficients of thermal expansion.